High‐Efficiency Quantum Defect Generation in Carbon Nanotubes via Oxygen‐Free Photochemistry

ABSTRACT Single‐walled carbon nanotubes (SWCNTs) offer potential for a wide range of applications from optoelectronic devices to biomedical diagnostics. One reason is their tunable optical properties, which can be tailored by introducing quantum defects. However, the chemical conditions to obtain an optimal number and specific type of quantum defect are difficult to control. Here, we demonstrate that oxygen‐free conditions are crucial to control the spectral features. To this end, we analyze the photochemical reaction of (6,5)‐SWCNTs with different alkyl/aryl halides and alkenyl/alkynyl compounds under UV irradiation. Removal of oxygen or addition of sulfites shifts the quantum defect‐related E 11 * emission peak from ∼1130 to ∼1100 nm, suggesting that different types of quantum defects are formed. For aryl halides, these conditions increase the E 11 */E 11 ratio up to 90%, while reducing the required reactant concentration by ∼90%, with reaction times < 10 min. For the less reactive alkyl halide, ∼80‐fold smaller reactant concentrations yielded similar E 11 */E 11 ratios compared to oxygen‐containing conditions. This allows us to investigate the combined effect of quantum defects and DNA functionalization of SWCNTs on small‐molecule detection. It underlines that efficient incorporation of quantum defects opens a new chemical dimension for SWCNT chemistry and enables control of fluorescence properties.